1. Field of the Invention
This invention relates to multicolor display devices utilizing light emitting diodes.
2. Description of the Prior Art
An electronic display having segments wherein each segment is capable of selectively illuminating two colors is disclosed in U.S. Pat. No. 4,488,149 issued on Dec. 11, 1984 to William A. Givens, Jr. Two AND gates are provided for biasing, in each display segment, either a first light emitting diode, for emitting a first color, or a second light emitting diode, for emitting a second color. It is not contemplated to illuminate both light emitting diodes in each segment simultaneously for blending the colors.
A multi-colour LED display for seven segment figures is disclosed in German Patent No. 3009416 issued on Sep. 17, 1981 to Klaus Gillessen. The LED circuit consists of seven group of diodes, each group made up of two diodes, one red and one green. The cathodes of all red diodes are terminated in a common connection, and the green ones likewise, the anodes of each pair of diodes being common for that pair. Two transistors connected in cascade are utilized for activating either all green LEDs, or all red LEDs, but not both simultaneously. When a low level signal is applied to the base of the first transistor, the first transistor is blocked, and the second transistor is turned ON to illuminate the second set of the diodes. When a high level signal is applied to the input of the first transistor, the first transistor is turned ON, while the second transistor is blocked, whereby the first set of the diodes is illuminated. Since the first transistor cannot be simultaneously turned ON and OFF, it would be impossible to illuminate the two sets of the diodes simultaneously. In another embodiment is shown a multi-colour LED display utilizing three sets of LEDs: red, green, and blue, which are respectively commonly connected and may be activated by manual switches. It is not contemplated that the three sets of LEDs be activated in selective combinations to blend the colors.
A digital electrooptical display with anti-parallel light emitting diodes is disclosed in East German Patent No. 220844 issued on Apr. 10, 1985 to Thomas Hoffman et al. Two light emitting diodes for emitting light of different colors are connected in each segment back-to-back. Since the light emitting diodes are connected to conduct currents in opposite directions, it would be impossible to illuminate them simultaneously, because the opposite currents would cancel.
It is the principal object of this invention to provide an improved multicolor display device.
It is another object of the invention to provide a multicolor display element using two primary color LEDs.
It is still another object of the invention to provide a multicolor display element using three primary color LEDs.
It is still another object of the invention to provide a multicolor display element in which the primary colors are selectively blended.
It is still another object of the invention to provide a multicolor display element in which the light emitting diodes for emitting light of different colors are respectively coupled to common electric paths called buses.
It is still another object of the invention to provide a multicolor display element in which the buses, to which the light emitting diodes of the same color are commonly coupled, may be activated in selected combinations.
It is still another object of the invention to provide a multicolor display element having three color control inputs.
It is still another object of the invention to provide a multicolor display element having seven color control inputs.
Other objects of the invention will be obvious from the appended drawings and their description.
In summary, a multicolor display element of the invention includes a plurality of display areas arranged in a pattern for selectively exhibiting a plurality of display units. Each display area includes two light emitting diodes, for emitting light signals of respectively different primary colors, and means for blending the light signals in each display area to obtain a composite light signal of a composite color. The light emitting diodes of the same color are respectively commonly coupled to two electric paths referred to as buses. The invention resides in providing a gate network for simultaneously activating the two buses by a single color control input, for blending the primary colors.
In another embodiment is disclosed a like multicolor display element using three light emitting diodes, for emitting light of respectively different primary colors, which are commonly coupled to three buses. The invention resides in the provision of a gate network for activating the three buses in selective combinations, for selectively blending the primary colors.